TY - JOUR
T1 - A Case Study of Transversely Heated Low-Energy Helium Ions by EMIC Waves in the Plasmasphere
AU - Kim, Khan Hyuk
AU - Kwon, Hyuck Jin
AU - Lee, Junhyun
AU - Jin, Ho
AU - Seough, Jungjoon
N1 - Publisher Copyright:
© 2021. The Authors.
PY - 2021/2
Y1 - 2021/2
N2 - The Van Allen Probe A spacecraft observed strong ∼0.5-Hz helium (He+) band and weak ∼0.8-Hz hydrogen (H+) band EMIC waves on April 17, 2018, at L = ∼4.5–5.2, in the dawn sector, near the magnetic equator, and close to the plasmapause. We examined low-energy ion fluxes observed by the Helium Oxygen Proton and Electron (HOPE) instrument onboard Van Allen Probe A during the wave interval and found that low-energy He+ flux (<10 eV) enhancements occur nearly simultaneously with He-band and H-band EMIC wave power enhancements in a direction mostly perpendicular to the background magnetic field without significant low-energy H+ and O+ flux variations. We suggest that cold He+ ions (<1 eV) are preferentially and transversely heated up 10 eV through the interaction with EMIC waves inside the plasmasphere. The low-Earth orbit spacecraft observed localized precipitations of energetic protons in the upper ionosphere at subauroral latitudes near the magnetic field footprint of Van Allen Probe A. Our observations provide a clear evidence that EMIC waves play an important role in the overall dynamics in the inner magnetosphere, contributing to the high-energy particle loss and low-energy particle energization.
AB - The Van Allen Probe A spacecraft observed strong ∼0.5-Hz helium (He+) band and weak ∼0.8-Hz hydrogen (H+) band EMIC waves on April 17, 2018, at L = ∼4.5–5.2, in the dawn sector, near the magnetic equator, and close to the plasmapause. We examined low-energy ion fluxes observed by the Helium Oxygen Proton and Electron (HOPE) instrument onboard Van Allen Probe A during the wave interval and found that low-energy He+ flux (<10 eV) enhancements occur nearly simultaneously with He-band and H-band EMIC wave power enhancements in a direction mostly perpendicular to the background magnetic field without significant low-energy H+ and O+ flux variations. We suggest that cold He+ ions (<1 eV) are preferentially and transversely heated up 10 eV through the interaction with EMIC waves inside the plasmasphere. The low-Earth orbit spacecraft observed localized precipitations of energetic protons in the upper ionosphere at subauroral latitudes near the magnetic field footprint of Van Allen Probe A. Our observations provide a clear evidence that EMIC waves play an important role in the overall dynamics in the inner magnetosphere, contributing to the high-energy particle loss and low-energy particle energization.
UR - http://www.scopus.com/inward/record.url?scp=85102135471&partnerID=8YFLogxK
U2 - 10.1029/2020JA028560
DO - 10.1029/2020JA028560
M3 - Article
AN - SCOPUS:85102135471
SN - 2169-9402
VL - 126
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
IS - 2
M1 - e2020JA028560
ER -